Field of the Invention
The present invention relates to an internal combustion engine.
Description of the Related Art
With regard to a cylinder of an internal combustion engine, a conventionally known technique forms a tumble flow that is a swirl flow in an axial direction of the cylinder. Formation of the tumble flow in the cylinder promotes mixing of the intake air with a fuel and thereby enhances the combustibility in the internal combustion engine.
Patent Literature 1 discloses a configuration of an intake port in the internal combustion engine having the tumble flow formed in the cylinder. According to this proposed configuration, when the intake port is divided into a cylinder center-side intake port area (upper area in the intake port in a side view of the intake port and the cylinder) which is an area on the cylinder center side and a cylinder outer peripheral-side intake port area (lower area in the intake port in the side view of the intake port and the cylinder) which is an area other than the cylinder center-side intake port area, the port radius of the cylinder outer peripheral-side intake port area is gradually varied in a neighborhood of an opening of the intake port to a combustion chamber. More specifically, an intake port expanded portion and an intake air adjusting portion are formed in the cylinder outer peripheral-side intake port area of the intake port. In the intake port expanded portion, the port radius of the cylinder outer peripheral-side intake port area is increased from upstream toward a location immediately upstream of the opening of the intake port to the combustion chamber in the neighborhood of the opening of the intake port to the combustion chamber. The intake air adjusting portion is, on the other hand, provided downstream of the intake port expanded portion to be extended to the opening of the intake port to the combustion chamber. In the intake air adjusting portion, the port radius of the cylinder outer peripheral-side intake port area is decreased from upstream toward the opening of the intake port to the combustion chamber. This intake air adjusting portion causes part of the flow of the intake air to be guided to the center of the intake port.
Patent Literatures 2 and 3 disclose other configurations of the intake port in the internal combustion engine having the tumble flow formed in the cylinder.